\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=stealth, thick,scale=1]
  \fill [pattern = north east lines] (0,-.25) rectangle (3, 0);
  \draw (0,0)--(3,0);
  \draw (.5, 5)node[left]{$A$}--(3,5);
  \draw (1, 1)node[below]{$C$}--(1.75,1);
  \draw [<-](1.25,1)--(1.25, 5);
  \draw [<->](1.5,0)--node [right]{\qty{3}{m}}(1.5,1);
  \draw [<->](1.5,1)--node [right]{\qty{12}{m}}(1.5, 5);
  \draw [<->](2.5, 5)--node [right]{\qty{15}{m}}(2.5,0);
  \draw[ultra thick] (.5, 5)--(.5,5.5);
  \draw[ultra thick] (.5+.5,5.5) arc (0:180:.25);
  \draw[ultra thick] (1,5.5)--(1,1);
  \node at (.75, 6){$B$};
  \draw [->](0,5)--node [left]{正方向}(0, 5.7);
  \pgfsetlinewidth{2pt}
  \pgfsetinnerlinewidth{1pt}
  \draw (0.25,0)--(.5, 5);
  \draw (0.75,0)--(.5, 5);
\end{tikzpicture}
\end{document}